To efficiently treat an imaging DTR element in a developing stage so as to eliminate difficulties in relation to the local consumption of a developer and to avoid irregular image quality by incorporating a flow controlling means into a developer circulating means.

This treating device is equipped with a developer tank 8. A trough 4 for developer is equipped with a feed bar or a spray bar having a slot which acts as a flow controlling means. An imaging element is supplied between driven feeding rollers 1 by making the face of an exposed side upward and guided by a first guide roller 3A to the trough 4 on a guide plate 6. A developer is taken out of the main body of a tank 8 by a circulating pump 7 and transferred to the bar and thereby, to the trough 4. The transportation rate of the developer by the circulating pump 7 is controlled by the length of the bar 5 and the dimension and the number of slots or spray nozzles of the bar. The developer is supplied through one end of the bar 5 to the bar 5.